Neurodegenerative disorders of aging result from cumulative neuronal damage due to direct toxic effects on neurons plus indirect glia- associated effects. Events common to many neurodegenerative processes are injury due to reactive oxygen species (ROS), such as nitric oxide, NO, and mitochondrial dysfunction. The lipid biomediator lysophosphatidic acid (LPA) is likely to participate in neurodegenerative diseases since: i) LPA causes neuronal death, ii) ROS including NO, and mitochondrial dysfunction are important in LPA-induced neurotoxicity, iii) LPA-induced astrocyte responses can enhance neuronal death, e.g., LPA stimulates astrocyte expression of inflammatory cytokines, and iv) the synthesis of LPA is stimulated by neurodegeneration-associated events. Based on these published and preliminary findings, it is proposed that the production of LPA is stimulated by neurotoxic and inflammatory events, and, in turn, LPA is neurotoxic and inflammatory. To evaluate this hypothesis, the specific aims are to: 1. characterize the increase in LPA levels in neurons, PC12 cells and astrocytes in response to injury-related signals, and 2. define the LPA-induced increase in astrocyte production of cytokines and determine the effect of LPA on astrocyte NO synthesis. The stimulation of LPA synthesis by H2O2 treated PC12 cells, glutamate or H2O2 treated neurons and cytokine treated astrocytes will be characterized by metabolic labeling of cells with 32Pi, treatment of cells and then lipid extraction, chromatography and quantification. The LPA-mediated stimulation of astrocyte production of cytokines will be determined at the RNA (reverse transcription-polymerase chain reaction) and protein (ELISA assays) levels. The potential stimulation of NO synthesis in astrocytes by LPA will be assessed by nitrite analysis (Griess reaction). These studies should i) define neuronal injury-associated events resulting in LPA synthesis and LPA-induced astrocyte responses which can contribute to neuronal death, and ii) serve as foundation for future studies, including the elucidation the in vivo roles of LPA in neurodegenerative disorders.